Control system for electrically operated circuit interrupters



Oct. 14, 1958 M. B. FORNWALT 2,855,565

CONTROL SYSTEM FOR ELECTRICALLY OPERATED CIRCUIT INTERRUPTERS Filed Dec.3, 1956 SE'CONDARY NETWORK PIP/MAR Y FEEDER Inventor:

Max B. Fornwalt,

CONTROL SYSTEM FOR ELECTRICALLY OPER- ATED CIRCUIT INTERRUPTERS Max B.Fornwalt, Springfield, Pa., assignor to General Electric Company, acorporation of New York Application December 3, 1956, Serial No. 625,680

6 Claims. (Cl. 317-22) This invention relates to control systems forelectrically operated circuit interrupters, and more particularly to animproved system for controlling the energization of the closingmechanism of an electric switch or circuit interrupter.

In conventional closing control systems for electrically operatedcircuit interrupters, it has been necessary to employ a cut-off switchto deenergize the closing mechanism at a critical moment during closingoperation, thereby to prevent excessive and harmful overtravel in themechanism. Precise adjustment of the cut-off switch is necessary in suchconventional systems, and this adds significantly to the manufacturingand maintenance costs of the interrupter. Accordingly, a general objectof this invention is the provision, for closing an electric circuitinterrupter, of a control system that does not require the use of acritically adjusted cut-ofi switch.

A further object of the invention is the provision, for closing anelectric circuit interrupter, of an improved control system whichprevents energization of the interrupter closing mechanism whenever theinterrupter is in its closed circuit position.

It is another object of the invention to provide an improved closingcontrol system employing an auxiliary relay which prevents energizationof the closing mechanism unless there is sufiicient voltage availablefor successfully completing the closing operation.

Another object of the invention is the provision of an improved closingcontrol system employing an auxiliary relay arranged to permit automaticreclosing operation of the circuit interrupter in response topredetermined circuit conditions, said auxiliary relay being energizedonly during the reclosing operation.

A further object is to provide an improved closing control system inwhich the circuitry is such that the contacts of the auxiliary relay arenot required to break the energizing current supplied to the closingmechanism.

Still another object is the provision, for a circuit interrupter havinga closing mechanism which converts electric energy into mechanicalenergy and utilizes the mechanical energy to close the interrupter, ofan improved control system for successfully performing a closingfunction independent of the value of supply voltage at the moment theinterrupter contacts make circuit.

In carrying out my invention in one form, I provide a control systemwhich is particularly well suited for controlling the closing of anelectric circuit interrupter having a closing mechanism that convertselectric energy into mechanical energy and utilizes the mechanicalenergy to close the interrupter. The interrupter also includes aposition indicating contact which opens as the interrupter moves towardits closed circuit position. My improved control system comprises anauxiliary relay which is energized in controlled response topredetermined circuit conditions including the open circuit condition ofthe interrupter. The auxiliary relay is provided with a sealin contactconnected to retain the relay energized as long as the interrupterremains open. I provide circuit means nited States Patent includinganother contact of the auxiliary relay and the position indicatingcontact of the interrupter to supply electric energy to the circuitinterrupter closing mechanism only while the interrupter is open and therelay is energized.

My invention will be better understood and further objects andadvantages will be apparent from the following description taken inconjunction with the accompanying drawing in which:

Fig. l is a schematic circuit diagram of a network system utilizing acircuit interrupter whose closing may be controlled in accordance withmy invention; and

Fig. 2 is a schematic representation of a circuit interrupter utilizinga closing control system in accordance with one embodiment of myinvention.

Referring now to Fig. 1, I have shown a segment of a 3-phase alternatingcurrent secondary network system in order to illustrate one practicalapplication for my improved circuit interrupter closing control system.The secondary network system is entirely conventional and will bedescribed only briefly herein. A grid of interconnected cables, labeledsecondary network in the drawing, is energized at utilization voltagefrom at least one primary feeder which is connected to the secondarynetwork at a plurality of points, only one of which has beenillustrated. Each interconnection between primary,

feeder and secondary network, as shown in the brokenline box 1 of Fig.1, comprises four integral components: a 3-pole isolating switch 2; a3-phase network transformer 3; a 3-pole electrically operated circuitinterrupter 4; and three suitable back-up fuses 5.

The circuit interrupter 4 has been shown schematically and onlypartially in Fig. 1, the details having been omitted here for the sakeof drawing simplicity. A mechanism particularly well suited for closingthe interrupter is illustrated in Fig. 2 and will be fully describedhereinafter. This closing mechanism, as well as the interrupter trippingmechanism which has not been shown, operates in response to closing andtripping signals supplied by suitable network relays represented in Fig.1 merely as a solid-line rectangle 6.

The network relays 6 may be of any suitable type, such as, for example,the combination of elements which are illustrated, described and claimedin U. S. Patent 1,971,810 issued to David K. Blake on August28, 1934. Bymeans of current transformers 7, 8 and 9, the network relays 6 areprovided with energization proportional to the current flowing throughthe closed contactsof interrupter 4 or, when the interrupter is open,with energization proportional to the voltage across the open contacts,this voltage being reflected in the aforesaid current transformers fromthe associated transformer windings 7', 8', and 9 which are connectedvia resistors 10, 11 and 12, respectively, between opposite terminals ofthe 3-pole interrupter. By means of the connections shown in Fig. 1, thenetwork relays are additionally provided with energization proportionalto the secondary network voltage and proportional to the voltage acrossthe secondary windings of the network transformer 3. The network relays6 in combination with the circuit interrupter 4 form a so-called networkprotector.

The illustrated network protector operates automatically as follows:Should electric power flow in a direction from secondary network toprimary feeder, such as during a short circuit or fault in a primaryfeeder, network relays 6 close an appropriate contact (not shown) toenergize the tripping mechanism of interrupter 4 thereby opening theinterconnecting circuit. The load circuits connected to the secondarynetwork are now supplied solely from the sound primary feeders whichremain connected to the secondary network. After the fault has beencorrected and as soon as the secondary cally reclosi-ng theinterrupter.- Electric power will now flow in the correct direction fromprimary feeder to secondary network. Whenever a secondary fault occurs,it will either burn itself clear or be isolated by suitable limiters(not shown) which are connected to the opposite ends of each section ofsecondary cable.

Turning now to Figure 2, I have shown schematically an electroresponsiveclosing mechanism for circuit interrupter 4. This closing mechanism, asillustrated by way of example, includes an electric motor driven, energystoring operating device indicated generally by the reference character15. The operating device 15, which may be of the improved type fullydisclosed and claimed in U. S. Patent 2,667,076 issued on January 26,1954, to John A. Favre, comprises an energy accumulator in the form of aheavy coil compression spring 16 having its upper end fixed against asuitable abutment 17 and its lower end engaging a spring seat 18 that ispivotally connected by means of a pin 19 to operate a bell crank 20 uponrelease of the mechanical energy stored in spring 16. The bell crank 20is fixed to a shaft 21 that carries an arm. 22 having a roller 23mounted at the end thereof for engaging a closing member 24 ofsequential closing linkages of the circuit interrupter 4.

The sequential closing linkages, which have been indicated in Fig. 2generally by the reference character 25,

may bev of the improved type fully described and claimed in U. S. Patent2,581,181, issued on January 1, 1952, to John A. Favre. As the energystored in the compression spring 16 is released to rotate the bell crank20 and thereby shaft 21 in a clockwise direction, roller 23 engages the.closing member 24 to tilt this member counterclockwise about its.intermediate pivotal point 26. Member 24 is moved to a position whereina pin 27 carried by it is engaged by a holding latch 28 pivoted on a pin29 and biased by a suitable spring 30 into latching relation in the pathof pin 27.

In moving toward its latched position, closing member 24 exerts forcethrough a toggle link 31 to pivot a main tension link 32 clockwise abouta point 32a to position wherein switch contacts are closed. By means ofthe various linkages shown, main tension link 32 carries a movable mainswitch contact 33 and a movable arcing contact 34 from their opencircuit or reset position shown in Fig. 2 to a closed circuit positionwherein they engage cooperating stationary main switch contact 35 andstationary arcing contact 36, respectively. An insulating crossarm 37disposed on main tension link 32 interconnects the similar main tensionlinks of the other two poles (not shown) of the 3-pole interrupter 4.

Before the closing operation described above can take place, bell crank20 must be rotated counterclockwise to compress the coil spring 16 andstore mechanical energy therein. This is accomplished by means of arotatable crank arm 38 which carries a cam roller 39 at its free end toconstitute an orbital element revolving in an orbital path to engagewith a flat cam surface 40 of the bell crank 20. Spring 16 ispractically fully compressed when the crank arm 38 is moved to thesubstantially dead center angular position in which it is shown in Fig.2, and further counterclockwise movement by the orbital element 'willcarry it overcenter to release the energy stored in compressed spring 16thereby closing the circuit interrupter as described. The crank arm 33is fixedly mounted upon the end of a shaft 41 which is rotated by meansof the improved difierential force amplifying overrunning drivemechanism 42 described and claimed in the aforementioned Patent2,667,076. The mechanism 42 is arranged to be driven by a relativelysmall electric motor 43, and my. improved control system is, utilizedto. control the energization' of this motor in accordance with theappropriate closing signal received from network relays 6.

As can be seen in Fig. 2, the closing control system includes anelectromagnetic auxiliary relay or switching means 44 having anactuating coil 45, a normally open seal-in contact 46 and a normallyopen main contact 47. The seal-in contact is shunted by a manuallyoperable push button control switch 48. The motor 43 is connected to apair of electric energy supply terminals 49 and by means of a circuitformed by main contact 47 which is serially connected to a positionindicating contact 51 of the circuit interrupter 4.

The position indicating switch or contact 51 is held in a first circuitcontrolling position with its contact closed against the force of a biasspring 52 by the main tension link 32 of the closing linkages 25whenever this link is in its open position, as is shown in Fig. 2. Thus,position indicating contact 51 is actuated to a second circuitcontrolling position with its contact open as the movable contacts 33and 34 of circuit interrupter 4 move. toward their closed circuitposition. In accordance with my invention, the exact point at whichcontact 51 opens during a closing operation isnot critical, as long asit opens after the main tension link 32 begins its closing movement butbefore the movable contacts reach a fully closed position.

The actuating coil 45 and seal-in contact 46 of auxiliary relay 44 areconnected in series circuit relationship between energizing terminal 49and position indicating contact 51. In other words, coil 45 and contact46 are connected across the series combination of driving motor 43 andauxiliary contact 47. The common connection between coil 45 and contact46 is designated terminal 53. Actuating coil 45 may be convenientlyselected to respond only to voltage of greater than a predeterminedmagnitude. This predetermined magnitude of voltage is sufficiently greatto energize properly the driving motor 43.

The terminals 49, 50 and 53 shown in Fig. 2 are also indicated inFig. 1. It will be observed that energizing terminals 49 and 50 areconnected to the secondary windings of network transformer 3 whichcomprises the source of electric energy for activating the closingmechanism of interrupter 4. Terminal 53 is coupled to terminal 49 bymeans of the series connected contacts 13 and 14 of the network relays6.

From the foregoing detailed description of the components and circuitryof my improved control system, its mode of operation may now be readilyfollowed. To close the circuit interrupter 4, actuating coil 45 ofauxiliary relay 44 is connected directly to the energizing terminal 49.This connection may be accomplished automatically by the closure ofnetwork relaycontacts 13 and 14 which are connected between terminals 49and 53, or manually by the closure of control switch 48. In either case,the resulting shunting of seal-in contact 46 will complete theenergizing circuit for the actuating coil 45 if the position indicatingcontact 51 is closed thus ensuring that the circuit interrupter 4 is inan open circuit condition. If the magnitude of voltage available atenergizing terminals 49 and 50 is greater than the aforesaidpredetermined magnitude, auxiliary relay 44 will operate to close itscontacts 46 and 47. It will be noted that the auxiliary relay 44 willnot operate during abnormally low voltage conditions, and thus drivingmotor 43 cannot be connected for energization by inadequate voltage.

The closure of seal-in contact 46 will retain actuating coil 45energized until position indicating contact 51 opens. The closure ofmain contact 47 completes the circuit which includes contact 51 forenergizing the closing motor 43 of the circuit interrupter closingmechanism, thereby initiating closing movement of the interrupter.Closing motor 43 operates through mechanism 42 to rotate crank arm 38counterclockwise and compress the coil spring 16. Thus electric energysupplied to the closing mechanism is converted into mechanical energywhich is stored in spring 16 and released as crank arm 38 moves past itsdead center position. Release of this stored energy rotates bell crank20 and shaft 21 in a clockwise direction to close the interruptercontacts 3336 as described hereinbefore. At some noncritical pointduring movement of the sequential closing linkages 25 to closedposition, position indicating contact 51 simultaneously breaks theenergizing circuits of driving motor 43 and auxiliary relay 44, andmotor 43 will now come to rest in readiness for the next closing cycle.Should the interrupter 4 be tripped while contacts 13 and 14 of networkrelays '6 remain closed, the closing operation just described willimmediately be repeated, and the interrupter will automatically reclose.

The force exerted by the closing mechanism on the movable interruptercontacts as they move toward their fully closed position is independentof the value of voltage supplied to the motor 43. If the interrupterwere closed on a faulted secondary feeder thereby temporarily reducingthe network transformer secondary voltage to a subnormal magnitude, theclosing mechanism will never theless successfully complete its closingoperation.

The period of time required to charge the closing mechanism during aclosing operation, i. e., the time which elapses while spring 16 isbeing compressed, presents no problem in the illustrated application ofmy control system. Since the secondary network and primary feeder areinterconnected through other network prorectors, not shown, these twoelectric circuits are already in synchronism, and delayed closing ofinterrupter 4 can be tolerated without any harmful effects.

While I have shown and described a preferred form of my invention by wayof illustration, many modifications will occur to those skilled in theart, I contemplate, therefore, by the claims which conclude thisspecification to cover all such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a control system for an electric circuit interrupter having amovable switch member and an electroresponsive closing mechanism formoving the switch member from an open circuit to a closed circuitposition, a relay actuatable when energized to close a contact, controlmeans connected to energize said relay in controlled response topredetermined circuit conditions, and means including said contactresponsive to the actuation of said relay to energize the closingmechanism and initiate circuit closing movement of the switch member,said closing mechanism energizing means including means operable inresponse to the closing movement of the switch member before reachingits closed circuit position to deenergize said closing mechanism.

2. In a system for controlling the energization of the closing mechanismof an electric switch having a posi tion indicating contact which isclosed while the switch is in its open position and which opens duringthe closing operation of the switch before the switch is closed, firstand second energizing terminals, means connecting the positionindicating contact to 'said first energizing terminal, an auxiliaryrelay having an actuating coil and a first normally open contactserially interconnected between said position indicating contact andsaid second terminal, said first normally open contact being adapted tobe shunted in order to initiate a closing operation, and circuit meansincluding a second normally open contact of said auxiliary relayconnecting the closing mechanism of the switch between said positionindicating contact and said second terminal, whereby said second contactwill close to activate said closing mechanism whenever said firstnormally open contact is shunted while the switch is open.

.3. In a system for controlling the closing of an elec-' trio circuitbreaker provided with an energy storing overrunning closing mechanismincluding a motor, an energy accumulator having a rotatable cam drivenby the motor for storing energy during a partial revolution of the camand for releasing the energy stored during the remainder of therevolution of the cam, and sequential closing linkages driven by theenergy accumulator to close the circuit breaker upon release of thestored energy: a position indicating contact coupled to the closinglinkages and operable from a closed to an open circuit position inresponse to the closing movement of said linkages, a pair of energizingterminals, switching means having an actuating coil and first and secondcontacts which are closed when the actuating coil is energized, saidfirst contact being connected in series circuit relationship with theclosing mechanism and the position indicating contact between saidenergizing terminals to permit energization of said closing mechanismonly when the circuit breaker is in an open circuit condition and saidactuating coil is energized, said second contact being connected inseries circuit relationship with said actuating coil and said positionindicating contact between said energizing terminals, and means shuntingsaid second contact to energize said actuating coil in controlledresponse to predetermined circuit conditions including the open circuitcondition of said circuit breaker.

4. A control system for an electric switch having a closing mechanismwhich operates to convert electric energy into mechanical energy and toutilize said mechanical energy for closing the switch and including aposition indicating contact which opens as the switch moves toward itsclosed circuit position during closing operation comprising, a pair ofelectric energy supply terminals, an electromagnetic relay having anactuating coil and including seal-in and main contacts which close whensaid actuating coil is energized, circuit means serially connecting saidmain contact, the closing mechanism and the position indicating contactbetween said terminals, means serially connecting said seal-in contactand said actuating coil across the series combination of said maincontact and said closing mechanism, and connections for shunting saidseal-in contact when closing operation is desired.

5. In a control system for an electric circuit interrupter having aswitch member movable between open circuit and closed circuit positionsand having a closing mechanism including electromechanical means forconverting electric energy into mechanical energy and utilizing themechanical energy to carry the switch member from open to closed circuitpositions: switching means operable to initiate operation of the closingmechanism; an auxiliary relay including a normally open contact and anactuating coil; a position indicating switch actuatable from first tosecond circuit controlling positions in response to closing movement ofsaid switch member before said switch member reaches its closed circuitposition; said position indicating switch in its first circuitcontrolling position having connections with said switching means forenergizing the actuating coil of said auxiliary relay in response tooperation of said switching means and having other connections with saidnormally open contact for activating said electromechanical means uponoperable energization of said actuating coil and for deactivating saidelectromechanical means upon actuation of said position indicat ingswitch to its second circuit controlling position.

6. In a control system for an electric circuit interrupter having aswitch member movable between reset and latched-closed positions andhaving a closing mechanism including electromechanical means forconverting electric energy into mechanical energy and utilizing themechanical energy to carry the switch member from reset tolatched-closed positions: an auxiliary relay; first and secondenergizing circuits respectively operable to energize saidelectromechanical means and said auxiliary relay; means for renderingsaid second energizing circuit operative to energize said auxiliaryrelay; contact means responsive to operable energization of saidauxiliary relay for rendering said first energizing circuit operative toenergize said electromechanical means; a position indicating switchconnected in both of said energizing circuits and operated by theclosing movement of said switch member before said switch member reachesits latchedclosed position for rendering said energizing circuitsinoperative and thereby deenergizing said electromechanical meansandsaid auxiliary relay.

References Cited in the file of-this patent UNITED STATES PATENTS KautzF 11111621,]1 '2 CIaZO Mar. 21, 193'3 Johnson- Dec. 2 194.1: ThurninFeb. 24-, 1942' Couggeshall et a1. Jan. 5, 19.43

